1. Field of the Invention
The present invention relates to an apparatus for manufacturing a float glass, and more particularly, to an apparatus for manufacturing a float glass using a float glass process.
2. Description of the Related Art
Generally, an apparatus for manufacturing a float glass (also known as a sheet glass, a flat glass or a plate glass) using a float glass process is used to manufacture a continuous sheet of glass having a ribbon shape of a predetermined width by continuously supplying a molten glass onto a flowing molten metal (a molten tin and so on) stored in a float bath while floating the molten glass on the molten metal to form a molten glass ribbon reaching around an equilibrium thickness due to the surface tension and gravity, and pulling up the molten glass ribbon toward an annealing lehr near an exit of the float bath.
Here, the molten metal includes, for example, a molten tin or a molten tin alloy, and has a greater specific gravity than the molten glass. The molten metal is received in a float chamber where a reducing atmosphere of hydrogen (H2) and/or nitrogen (N2) gas is introduced. The float bath in the float chamber is configured to contain the molten metal therein. The float bath has a horizontally extending structure, and includes a high heat resistant material (for example, bottom blocks) therein. The molten glass forms a molten glass ribbon on the surface of the molten metal while moving from an upstream end of the float bath to a downstream end. The molten glass ribbon is lifted up at a location set on the downstream end of the float bath, so called a take-off point, to be removed from the molten metal, and delivered to an annealing lehr of a next process.
However, because the molten metal in the float chamber is in a high-temperature state (for example, about 600 to 1100° C.), chemical reactions take place among the molten metal, the molten glass, H2 and N2 of the atmosphere, a very small amount of O2, H2O and S to generate impurities that are referred to as “dross”. In particular, temperature is lower at and around the take-off point on the downstream end (Cold End) of the float bath than the upstream end (Hot End). Thus, solubility of the molten metal decreases on the downstream end, and consequently, metal oxide dross, for example SnO2, etc. is liable to happen and accumulate on the downstream end. When the molten glass ribbon is lifted up from the take-off point, the dross is attached to the bottom of the molten glass ribbon and drawn from the float bath, accompanied by the molten glass ribbon. As a result, it causes scratch, stain and so on that may unfavorably influence a subsequent process and/or the quality of float glass products.
To solve the problems, various techniques have been developed so far. For example, as disclosed in Japanese Patent Publication No. SO45-30711, a conventional apparatus for manufacturing a float glass includes a collecting channel having an approximately T-shaped pocket of which a plane expands slightly in a widthwise direction by a side wall and a rear wall of a longitudinal end portion of a float bath. The collecting channel is formed at a predetermined angle so that dross gathered in the collecting channel from an exposed drainage area can be guided to the pocket. The dross is discharged from the pocket outside the float bath.
As disclosed in Japanese Patent Laid-open Publication No. 2000-128552, another conventional apparatus for manufacturing a float glass includes a first flow channel extending in a cross direction with respect to a draw-out direction of the float glass, and a second flow channel connected to an end of the first flow channel and communicated with a dam starting from the outside of a side wall. The apparatus flows back a molten metal from a downstream end of a float bath to an upstream end through separate flow channels.
However, these conventional techniques remove dross, which was caused by contamination in a float bath, at both sides of a downstream end of the float bath. However, the conventional techniques have difficulty in removing dross accumulated under the center of a molten glass ribbon at the downstream end, and to remove such dross, it should open a side sealing with a separate strap-shaped tool made of wood. Under this operational environment, when the side sealing is open, the float bath may be further contaminated and safety in operation may be not guaranteed. As a result, it may deteriorate the quality of float glass products and the procedural stability.